<!DOCTYPE html>
<html lang='en'>

<head>
    <meta charset='UTF-8' />
    <meta name='viewport' content='width=device-width, initial-scale=1.0' />
    <title>Document</title>
    <script src='../js/vue.js'></script>
</head>

<body>
    <div id='root'>
        姓：<input type="text" v-model="firstName" />
        <br>
        名：<input type="text" v-model="lastName" />
        <br>
        全名：<span>{{firstName.slice(0,3)}} {{lastName}}</span>
    </div>
    <script>
        const vm = new Vue({
            el: '#root',
            data: {
                firstName: "张",
                lastName: "三"
            },
        });
    </script>
</body>

</html>